diff --git a/app/Article.py b/app/Article.py
index 04a32ea..707ad91 100644
--- a/app/Article.py
+++ b/app/Article.py
@@ -32,12 +32,14 @@ def get_article_body(s):
     return '\n'.join(lst)
 
 
-def get_today_article(user_word_list, articleID):
+def get_today_article(user_word_list, existing_articles):
     rq = RecordQuery(path_prefix + 'static/wordfreqapp.db')
-    if articleID == None:
+    if existing_articles is None:
+        existing_articles = [0, []]  # existing_articles[0]：为existing_articles[1]的索引；existing_articles[1]:之前显示文章的id列表，越后越新
+    if existing_articles[0] > len(existing_articles[1])-1:
         rq.instructions("SELECT * FROM article")
     else:
-        rq.instructions('SELECT * FROM article WHERE article_id=%d' % (articleID))
+        rq.instructions('SELECT * FROM article WHERE article_id=%d' % (existing_articles[1][existing_articles[0]]))
     rq.do()
     result = rq.get_results()
     random.shuffle(result)
@@ -50,33 +52,39 @@ def get_today_article(user_word_list, articleID):
     d = {}
     d_user = load_freq_history(user_word_list)
     user_level = user_difficulty_level(d_user, d3)  # more consideration as user's behaviour is dynamic. Time factor should be considered.
-    random.shuffle(result)  # shuffle list
-    d = random.choice(result)
-    text_level = text_difficulty_level(d['text'], d3)
-    if articleID == None:
+    text_level = 0
+    flag = False
+    if existing_articles[0] > len(existing_articles[1])-1:  # 下一篇
         for reading in result:
             text_level = text_difficulty_level(reading['text'], d3)
             factor = random.gauss(0.8,
                                   0.1)  # a number drawn from Gaussian distribution with a mean of 0.8 and a stand deviation of 1
-            if within_range(text_level, user_level, (8.0 - user_level) * factor):
+            if within_range(reading['article_id'] not in existing_articles[1] and text_level, user_level, (8.0 - user_level) * factor):  # 新的文章之前没有出现过且符合一定范围的水平
                 d = reading
+                existing_articles[1].append(d['article_id'])  # 列表添加新的文章id；下面进行
+                flag = True
                 break
+    else:  # 上一篇
+        d = random.choice(result)
+        text_level = text_difficulty_level(d['text'], d3)
+        flag = True
 
-    s = '<div class="alert alert-success" role="alert">According to your word list, your level is <span class="badge bg-success">%4.2f</span>  and we have chosen an article with a difficulty level of <span class="badge bg-success">%4.2f</span> for you.</div>' % (
-        user_level, text_level)
-    s += '<p class="text-muted">Article added on: %s</p>' % (d['date'])
-    s += '<div class="p-3 mb-2 bg-light text-dark">'
-    article_title = get_article_title(d['text'])
-    article_body = get_article_body(d['text'])
-    s += '<p class="display-5">%s</p>' % (article_title)
-    s += '<p class="lead"><font id="article" size=2>%s</font></p>' % (article_body)
-    s += '<p><small class="text-muted">%s</small></p>' % (d['source'])
-    s += '<p><b>%s</b></p>' % (get_question_part(d['question']))
-    s = s.replace('\n', '<br/>')
-    s += '%s' % (get_answer_part(d['question']))
-    s += '</div>'
-    session['articleID'] = d['article_id']
-    return s
+    today_article = None
+    if flag:
+        today_article = {
+            "user_level": '%4.2f' % user_level,
+            "text_level": '%4.2f' % text_level,
+            "date": d['date'],
+            "article_title": get_article_title(d['text']),
+            "article_body": get_article_body(d['text']),
+            "source": d["source"],
+            "question": get_question_part(d['question']),
+            "answer": get_answer_part(d['question'])
+        }
+    else:
+        existing_articles[0] -= 1
+
+    return existing_articles, today_article
 
 
 def load_freq_history(path):
@@ -116,21 +124,4 @@ def get_answer_part(s):
             flag = 1
         elif flag == 1:
             result.append(line)
-    # https://css-tricks.com/snippets/javascript/showhide-element/
-    js = '''
-<script type="text/javascript">
-
-    function toggle_visibility(id) {
-       var e = document.getElementById(id);
-       if(e.style.display == 'block')
-          e.style.display = 'none';
-       else
-          e.style.display = 'block';
-    }
-</script>
-    '''
-    html_code = js
-    html_code += '\n'
-    html_code += '<button onclick="toggle_visibility(\'answer\');">ANSWER</button>\n'
-    html_code += '<div id="answer" style="display:none;">%s</div>\n' % ('\n'.join(result))
-    return html_code
\ No newline at end of file
+    return '\n'.join(result)
\ No newline at end of file
diff --git a/app/account_service.py b/app/account_service.py
index 9b1c46b..c1bd64c 100644
--- a/app/account_service.py
+++ b/app/account_service.py
@@ -19,21 +19,15 @@ def signup():
         # POST方法需判断是否注册成功，再根据结果返回不同的内容
         username = escape(request.form['username'])
         password = escape(request.form['password'])
-        password2 = escape(request.form['password2'])
         
         #! 添加如下代码为了过滤注册时的非法字符
         warn = WarningMessage(username)
         if str(warn) != 'OK':
-            return str(warn)
+            return jsonify({'status': '3', 'warn': str(warn)})
         
         available = check_username_availability(username)
         if not available: # 用户名不可用
-            flash('用户名 %s 已经被注册。' % (username))
-            return render_template('signup.html')
-        elif len(password.strip()) < 4: # 密码过短
-            return '密码过于简单。'
-        elif password != password2:
-            return '确认密码与输入密码不一致！'
+            return jsonify({'status': '0'})
         else: # 添加账户信息
             add_user(username, password)
             verified = verify_user(username, password)
@@ -43,11 +37,10 @@ def signup():
                 session[username] = username
                 session['username'] = username
                 session['expiry_date'] = get_expiry_date(username)
-                session['articleID'] = None
-                return '<p>恭喜，你已成功注册， 你的用户名是 <a href="%s">%s</a>。</p>\
-                <p><a href="/%s">开始使用</a> <a href="/">返回首页</a><p/>' % (username, username, username)
+                session['existing_articles'] = None
+                return jsonify({'status': '2'})
             else:
-                return '用户名密码验证失败。'
+                return jsonify({'status': '1'})
 
 
 
@@ -59,13 +52,7 @@ def login():
     '''
     if request.method == 'GET':
         # GET请求
-        if not session.get('logged_in'):
-            # 未登录，返回登录页面
-            return render_template('login.html')
-        else:
-            # 已登录，提示信息并显示登出按钮
-            return '你已登录 <a href="/%s">%s</a>。 登出点击<a href="/logout">这里</a>。' % (
-                session['username'], session['username'])
+        return render_template('login.html')
     elif request.method == 'POST':
         # POST方法用于判断登录是否成功
         # check database and verify user
@@ -79,10 +66,10 @@ def login():
             session['username'] = username
             user_expiry_date = get_expiry_date(username)
             session['expiry_date'] = user_expiry_date
-            session['articleID'] = None
-            return redirect(url_for('user_bp.userpage', username=username))
+            session['existing_articles'] = None
+            return jsonify({'status': '1'})
         else:
-            return '无法通过验证。'
+            return jsonify({'status': '0'})
 
 
 @accountService.route("/logout", methods=['GET', 'POST'])
@@ -115,31 +102,9 @@ def reset():
         # POST请求用于提交修改后信息
         old_password = escape(request.form['old-password'])
         new_password = escape(request.form['new-password'])
-
-        re_new_password = escape(request.form['re-new-password'])  # 确认新密码
-        if re_new_password != new_password: #验证新密码两次输入是否相同
-            return '新密码不匹配，请重新输入'
-        if len(new_password) < 4: #验证新密码长度，原则参照注册模块
-            return '密码过于简单。(密码长度至少4位)'
-
         flag = change_password(username, old_password, new_password) # flag表示是否修改成功
         if flag:
             session['logged_in'] = False
-            return \
-'''
-<script>
-alert('密码修改成功，请重新登录。');
-window.location.href="/login";
-</script>
-
-'''
-
+            return jsonify({'status':'1'})  # 修改成功
         else:
-            return \
-'''
-<script>
-alert('密码修改失败');
-window.location.href="/reset";
-</script>
-
-'''
+            return jsonify({'status':'2'})  # 修改失败
diff --git a/app/main.py b/app/main.py
index e311bb0..59e0b88 100644
--- a/app/main.py
+++ b/app/main.py
@@ -39,8 +39,7 @@ def get_random_ads():
     返回随机广告
     :return: 一个广告(包含HTML标签)
     '''
-    ads = random.choice(['个性化分析精准提升', '你的专有单词本', '智能捕捉阅读弱点，针对性提高你的阅读水平'])
-    return ads + '。 <a href="/signup">试试</a>吧！'
+    return random.choice(['个性化分析精准提升', '你的专有单词本', '智能捕捉阅读弱点，针对性提高你的阅读水平'])
 
 
 def appears_in_test(word, d):
diff --git a/app/templates/login.html b/app/templates/login.html
index a347e22..ccf6f34 100644
--- a/app/templates/login.html
+++ b/app/templates/login.html
@@ -1,28 +1,47 @@
 {% block body %}
 {% if session['logged_in'] %}
 
-You're logged in already!
+你已登录 <a href="/{{ session['username'] }}">{{ session['username'] }}</a>。 登出点击<a href="/logout">这里</a>。
 
 {% else %}
 <meta charset="utf-8" name="viewport" content="width=device-width, initial-scale=1.0, minimum-scale=0.5, maximum-scale=3.0, user-scalable=yes" />
 <link rel="stylesheet" href="static/css/login_service.css">
-
+<script src="static/js/jquery.js"></script>
+<script>
+    function login(){
+        let username = $("#username").val();
+        let password = $("#password").val();
+        if (username === "" || password === ""){
+            alert('输入不能为空!');
+            return false;
+        }
+        $.post(
+            "/login", {'username': username, 'password': password},
+            function (response) {
+                if (response.status === '0') {
+                    alert('无法通过验证。');
+                    window.location.href = "/login";
+                } else if (response.status === '1') {
+                    window.location.href = "/"+username;
+                }
+            }
+        )
+        return false;
+    }
+</script>
 <div class="container">
 
   <section class="signin-heading">
     <h1>Sign In</h1>
   </section>
 
-  <form action="/login" method="POST">
-    <input type="text" placeholder="用户名" class="username" name="username" required>
-    <input type="password" placeholder="密码" class="password"  name="password" required>
-    <button type="submit" class="btn">登录</button>
-  </form>
+  <input type="text" placeholder="用户名" class="username" id="username">
+  <input type="password" placeholder="密码" class="password"  id="password">
+  <button type="button" class="btn" onclick="login()">登录</button>
+  <a class="signup" href="/signup">注册</a>
 
 </div>
 
-<a href="/signup" class="signup">注册</a>
-
 {% endif %}
 {% endblock %}
 
diff --git a/app/templates/mainpage_get.html b/app/templates/mainpage_get.html
index cbb51a6..7f02c12 100644
--- a/app/templates/mainpage_get.html
+++ b/app/templates/mainpage_get.html
@@ -26,7 +26,7 @@
             <a href="/{{session['username']}}">{{session['username']}}</a></p>
         {% else %}
             <p><a href="/login">登录</a>  <a href="/signup">注册</a> <a href="/static/usr/instructions.html">使用说明</a></p >
-            <p><b>{{random_ads|safe}}</b></p>
+            <p><b> {{ random_ads }}。 <a href="/signup">试试</a>吧！</b></p>
         {% endif %}
         <div class="alert alert-success" role="alert">共有文章 <span class="badge bg-success"> {{number_of_essays}} </span> 篇</div>
         <p>粘贴1篇文章 (English only)</p>
diff --git a/app/templates/reset.html b/app/templates/reset.html
index 902d046..d29855b 100644
--- a/app/templates/reset.html
+++ b/app/templates/reset.html
@@ -2,6 +2,38 @@
     <meta charset="utf-8" name="viewport"
           content="width=device-width, initial-scale=1.0, minimum-scale=0.5, maximum-scale=3.0, user-scalable=yes"/>
     <link rel="stylesheet" href="static/css/login_service.css">
+    <script src="static/js/jquery.js"></script>
+    <script>
+        function reset() {
+            let old_password = $("#old-password").val();
+            let new_password = $("#new-password").val();
+            let re_new_password = $("#re-new-password").val();
+            if (old_password === "" || new_password === "" || re_new_password === ""){
+                alert('输入不能为空!');
+                return false;
+            }
+            if (new_password !== re_new_password) {
+                alert('新密码不匹配，请重新输入');
+                return false;
+            }
+            if (new_password.length < 4) {
+                alert('密码过于简单。(密码长度至少4位)');
+                return false;
+            }
+            $.post("/reset", {'old-password': old_password, 'new-password': new_password},
+                function (response) {
+                    if (response.status === '1') {
+                        alert('密码修改成功，请重新登录。');
+                        window.location.href = "/login";
+                    } else if (response.status === '2') {
+                        alert('密码修改失败');
+                        window.location.href = "/reset";
+                    }
+                }
+            )
+            return false;
+        }
+    </script>
 
     <div class="container">
 
@@ -9,14 +41,11 @@
             <h1>Reset Password</h1>
         </section>
 
-        <form action="/reset" method="POST">
-            <input type="password" placeholder="原密码" class="old-password" name="old-password" required>
-            <input type="password" placeholder="新密码" class="new-password" name="new-password" required>
-            <input type="password" placeholder="确认新密码" class="re-new-password" name="re-new-password" required>
-            <input type="submit" name="submit" class="btn" value="提交"/>
-            <input type="button" name="submit" class="btn" value="放弃修改"
-                   onclick="window.location.href='/{{ username }}'"/>
-        </form>
+        <input type="password" placeholder="原密码" class="old-password" name="old-password" id="old-password"/>
+        <input type="password" placeholder="新密码" class="new-password" name="new-password" id="new-password"/>
+        <input type="password" placeholder="确认新密码" class="re-new-password" name="re-new-password" id="re-new-password"/>
+        <button id="submit" class="btn" onclick="reset()">提交</button>
+        <button class="btn" onclick="window.location.href='/{{ username }}'">放弃修改</button>
 
     </div>
 {% endblock %}
\ No newline at end of file
diff --git a/app/templates/signup.html b/app/templates/signup.html
index 1fd05f0..c70e4ba 100644
--- a/app/templates/signup.html
+++ b/app/templates/signup.html
@@ -6,6 +6,47 @@ You're logged in already! <a href="/logout">Logout</a>.
 {% else %}
 <meta name="viewport" content="width=device-width, initial-scale=1.0, minimum-scale=0.5, maximum-scale=3.0, user-scalable=yes" />
 <link rel="stylesheet" href="static/css/login_service.css">
+<script src="static/js/jquery.js"></script>
+    <script>
+        function signup() {
+            let username = $("#username").val();
+            let password = $("#password").val();
+            let password2 = $("#password2").val();
+            if (username === "" || password === "" || password2 === ""){
+                alert('输入不能为空!');
+                return false;
+            }
+            if (password !== password2) {
+                alert('确认密码与输入密码不一致！');
+                return false;
+            }
+            if (password.length < 4) {
+                alert('密码过于简单。(密码长度至少4位)');
+                return false;
+            }
+            $.post("/signup", {'username': username, 'password': password},
+                function (response) {
+                    if (response.status === '0') {
+                        alert('用户名'+username+'已经被注册。');
+                        window.location.href = "/signup";
+                    } else if (response.status === '1') {
+                        alert('用户名密码验证失败。');
+                        window.location.href = "/signup";
+                    } else if (response.status === '2') {
+                        let f = confirm("恭喜，你已成功注册，你的用户名是"+username+'.\n点击“确认”开始使用，或点击“取消”返回首页');
+                        if (f) {
+                            window.location.href = '/'+username;
+                        } else {
+                            window.location.href = '/';
+                        }
+                    } else if (response.status === '3') {
+                        alert(response.warn);
+                    }
+                }
+            )
+            return false;
+        }
+    </script>
 <p>{{ get_flashed_messages()[0] | safe }}</p>
 
 
@@ -15,12 +56,10 @@ You're logged in already! <a href="/logout">Logout</a>.
     <h1>Sign Up</h1>
   </section>
 
-  <form action="/signup" method="POST">
-    <p><input type="username" name="username" placeholder="输入用户名" required="required" class="username"></p>
-    <p><input type="password" name="password" placeholder="输入密码" required="required" class="password"></p>
-    <p><input type="password" name="password2" placeholder="确认密码" required="required" class="password" ></p>
-    <button type="submit" class="btn">注册</button>
-  </form>
+  <p><input type="username" id="username" placeholder="输入用户名" class="username"></p>
+  <p><input type="password" id="password" placeholder="输入密码" class="password"></p>
+  <p><input type="password" id="password2" placeholder="确认密码" class="password" ></p>
+  <button type="button" class="btn" onclick="signup()">注册</button>
 
 </div>
   
diff --git a/app/templates/userpage_get.html b/app/templates/userpage_get.html
index ea91c58..5ef86c7 100644
--- a/app/templates/userpage_get.html
+++ b/app/templates/userpage_get.html
@@ -18,17 +18,6 @@
         {% endfor %}
     {% endif %}
 
-{#     // add !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!  #}
-    <script type="text/javascript">
-        function fresh() {
-            try {
-                document.getElementById('rv').click();
-            } catch {
-
-            }
-        }
-    </script>
-{#     !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! #}
     <title>EnglishPal Study Room for {{ username }}</title>
 
     <style>
@@ -45,31 +34,49 @@
         }
     </style>
 </head>
-{#   original code: <body>  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! #}
-<body onload="fresh()">
+<body>
 <div class="container-fluid">
     <p><b>English Pal for <font id="username" color="red">{{ username }}</font></b>
         <a class="btn btn-secondary" href="/logout" role="button">退出</a>
         <a class="btn btn-secondary" href="/reset" role="button">重设密码</a>
     </p>
-    {{ flashed_messages|safe }}
+    {% for message in messages %}
+        <div class="alert alert-warning" role="alert">Congratulations! {{ message }}</div>
+    {% endfor %}
 
     <a class="btn btn-success" href="/{{ username }}/reset" role="button"> 下一篇 Next Article </a>
-{#  add code !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!  #}
-    {% if session.get('articleID') == session.get('old_articleID') %}
-        {% if session.get('old_articleID') != None %}
-            <a class="btn btn-success" href="/{{ username }}/reset" role="button" id="rv"> 出bug了 </a>
-        {% endif %}
+    {% if session.get('existing_articles')[0] != None and session.get('existing_articles')[0] !=0 %}
+        <a class="btn btn-success" href="/{{ username }}/back" role="button"> 上一篇 Previous Article </a>
     {% endif %}
-    {% if session.get('articleID') != session.get('old_articleID') %}
-        {% if session.get('old_articleID') != None %}
-            <a class="btn btn-success" href="/{{ username }}/back" role="button"> 上一篇 Previous Article </a>
-        {% endif %}
-    {% endif %}
-{# !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!  #}
 
     <p><b>阅读文章并回答问题</b></p>
-    <div id="text-content">{{ today_article|safe }}</div>
+    <div id="text-content">
+        {% if today_article %}
+            <div class="alert alert-success" role="alert">According to your word list, your level is <span class="badge bg-success">{{ today_article["user_level"] }}</span>  and we have chosen an article with a difficulty level of <span class="badge bg-success">{{ today_article["text_level"] }}</span> for you.</div>
+                <p class="text-muted">Article added on: {{ today_article["date"] }}</p><br/>
+            <div class="p-3 mb-2 bg-light text-dark"><br/>
+            <p class="display-5">{{ today_article["article_title"] }}</p><br/>
+            <p class="lead"><font id="article" size=2>{{ today_article["article_body"] }}</font></p><br/>
+            <p><small class="text-muted">{{ today_article['source'] }}</small></p><br/>
+            <p><b>{{ today_article['question'] }}</b></p><br/>
+                <script type="text/javascript">
+                    function toggle_visibility(id) { {# https://css-tricks.com/snippets/javascript/showhide-element/#}
+                        const e = document.getElementById(id);
+                        if(e.style.display === 'block')
+                            e.style.display = 'none';
+                        else
+                            e.style.display = 'block';
+                    }
+                </script>
+                <button onclick="toggle_visibility('answer');">ANSWER</button>
+                <div id="answer" style="display:none;">{{ today_article['answer'] }}</div><br/>
+            </div>
+        {% else %}
+            <div class="alert alert-success" role="alert">
+                <p class="text-muted"><span class="badge bg-success">Notes:</span><br>No article is currently available for you. You can try again a few times or mark new words in the passage to improve your level.</p>
+            </div>
+        {% endif %}
+    </div>
 
     <input type="checkbox" onclick="toggleHighlighting()" checked/>生词高亮
     <input type="checkbox" onclick="onReadClick()" checked/>大声朗读
diff --git a/app/user_service.py b/app/user_service.py
index 2d10404..2c91391 100644
--- a/app/user_service.py
+++ b/app/user_service.py
@@ -29,9 +29,10 @@ def user_reset(username):
     :param username: 用户名
     :return: 返回页面内容
     '''
-    session['old_articleID'] = session.get('articleID')
     if request.method == 'GET':
-        session['articleID'] = None
+        existing_articles = session.get("existing_articles")
+        existing_articles[0] += 1
+        session["existing_articles"] = existing_articles
         return redirect(url_for('user_bp.userpage', username=username))
     else:
         return 'Under construction'
@@ -44,7 +45,9 @@ def user_back(username):
     :return: 返回页面内容
     '''
     if request.method == 'GET':
-        session['articleID'] = session.get('old_articleID')
+        existing_articles = session.get("existing_articles")
+        existing_articles[0] -= 1
+        session["existing_articles"] = existing_articles
         return redirect(url_for('user_bp.userpage', username=username))
 
 
@@ -130,11 +133,14 @@ def userpage(username):
         words = ''
         for x in lst3:
             words += x[0] + ' '
+        existing_articles, today_article = get_today_article(user_freq_record, session.get('existing_articles'))
+        session['existing_articles'] = existing_articles
+        # 通过 today_article，加载前端的显示页面
         return render_template('userpage_get.html',
                                username=username,
                                session=session,
-                               flashed_messages=get_flashed_messages_if_any(),
-                               today_article=get_today_article(user_freq_record, session['articleID']),
+                               flashed_messages=get_flashed_messages(),
+                               today_article=today_article,
                                d_len=len(d),
                                lst3=lst3,
                                yml=Yaml.yml,
@@ -173,15 +179,3 @@ def get_time():
     '''
     return datetime.now().strftime('%Y%m%d%H%M')  # upper to minutes
 
-def get_flashed_messages_if_any():
-    '''
-    在用户界面显示黄色提示信息
-    :return: 包含HTML标签的提示信息
-    '''
-    messages = get_flashed_messages()
-    s = ''
-    for message in messages:
-        s += '<div class="alert alert-warning" role="alert">'
-        s += f'Congratulations! {message}'
-        s += '</div>'
-    return s